Method of chemically crosslinking unsaturated polymers

ABSTRACT

This invention is a method of curing unsaturated polymers which do not have a significant amount of functional groups which undergo a cross-linking reaction with amino resins and which preferably comprise at least one conjugated diolefin monomer, said method comprising mixing said polymer with an amino resin in the presence of a proton-donating acid catalyst.

This is a division, of application Ser. No. 558,370, filed Jul. 27,1990, now U.S. Pat. No. 5,124,405.

BACKGROUND OF THE INVENTION

This invention relates to a novel method of crosslinking unsaturatedblock polymers. These polymers contain a tertiary carbon atom and mayespecially be polymers of conjugated diene monomers. Additionally, itrelates to novel polymers made by the claimed method and adhesives andsealants made with the polymers.

It is known that a polymer can be obtained by an anionic polymerizationof a conjugated diene compound or copolymerization with another diene oran alkenyl arene compound by using an organic alkali metal initiator.Thus, homopolymers and random and block copolymers can be made. Blockcopolymers have been produced which comprise primarily those having ageneral structure

    A--B and A--B--A

wherein the polymer blocks A comprise thermoplastic polymer blocks ofalkenyl arenes such as polystyrene, while block B is a polymer block ofa conjugated diene. The proportion of the thermoplastic blocks to theelastomeric polymer block and the relative molecular weights of each ofthese blocks is balanced to obtain a rubber having unique performancecharacteristics. When the content of the alkenyl arene is small, theproduced block copolymer is a so-called thermoplastic rubber. In such arubber, the blocks A are thermodynamically incompatible with the blocksB resulting in a rubber consisting of two phases; a continuouselastomeric phase (blocks B) and a basically discontinuous hard,glass-like plastic phase (blocks A) called domains. Since the A--B--Ablock copolymers have two A blocks separated by a B block, domainformation results in effectively locking the B blocks and their inherententanglements in place by the A blocks and forming a network structure.

These domains act as physical crosslinks anchoring the ends of manyblock copolymer chains. Such a phenomena allows the A--B--A rubber tobehave like a conventionally vulcanized rubber in the unvulcanized stateand is applicable for various uses. For example, these network formingpolymers are applicable for uses such as moldings of shoe soles, impactmodifiers for polystyrene resins and engineering thermoplastics, inadhesive and binder formulations and in the modification of asphalt.

Conversely, as the A--B block copolymers have only one A block, domainformation of the A blocks does not lock in the B blocks and theirinherent entanglements. Moreover, when the alkenyl arene content issmall resulting in a continuous elastomeric B phase, the strength ofsuch polymers is derived primarily from the inherent entanglements ofthe various B blocks therein and to a lesser extent the inherententanglements of the A blocks therein. Other non-network-formingpolymers include homopolymers of conjugated dienes and copolymers of atleast two conjugated dienes.

Both the network forming and non-network forming polymers are physicallycrosslinked. Light covalent crosslinking can be used to reinforce thephysical crosslinking already present in such polymers and makes thesepolymers less susceptible to property losses at high temperature or inthe presence of solvents and plasticizers. This allows them to be usedin a broader array of applications such as high temperature maskingtapes, permanent automotive tapes and sealants and permanent laminatingadhesives.

Such reinforcing crosslinking can be achieved by radiation curing.However, radiation curing has certain disadvantages including thenecessity for additional expensive equipment when EB processing orphotoinitiation and acrylic monomers when using UV. If chemicalcrosslinking could be utilized, certain of these disadvantages could beeliminated. Amino resins have been widely used to crosslink variouspolymers and resins. However, up to the present time it has been thoughtthat chemical crosslinking could only be achieved in polymers and resinswhich contained carboxyl groups or other functional groups. Forinstance, see 50 Years of Amino Coating Resins, edited and written byAlbert J. Kirsch, published in 1986 by American Cyanamid Company, whichdescribes in detail a whole series of amino resins which are useful inthe present invention. It is stated therein on page 20 that the backbonepolymers, i.e., the polymers which are to be crosslinked, "must containone or more of the functional groups--hydroxy, carboxy, amide--listedabove to be useful with amino resins". The foregoing publication isherein incorporated by reference. I have unexpectedly found that I cancarry out crosslinking of the unfunctionalized unsaturated polymersdescribed below using such chemical agents.

SUMMARY OF THE INVENTION

The present invention is a method of curing unsaturated polymers whichdo not have a significant amount of functional groups which undergo acrosslinking reaction with amino resins and which have a double bondbetween a tertiary carbon atom and another carbon and especiallypolymers which comprise at least one conjugated diolefin monomer. Thepolymer is mixed with the amino resin in the presence of aproton-donating acid catalyst. The preferred polymers comprise at leastone block A which comprises predominantly monoalkenyl aromatichydrocarbon monomer units and at least one block B which comprisespredominantly conjugated diolefin monomer units.

The amount of amino resin used generally ranges from about 0.5 to 40% ofthe weight of the polymer and the preferred amino resins for use in thepresent invention are glycoluril-formaldehyde resin andurea-formaldehyde resin. The amount of acid catalyst used generallyranges from about 0.1 to about 4% of the weight of the polymer. Thepresent invention also relates to a cured polymer made according to themethod described above. Finally, the invention relates to an adhesive orsealant made with such a cured polymer.

DETAILED DESCRIPTION OF THE INVENTION

Any polymer containing a double bond between a tertiary carbon atom andanother carbon may be crosslinked according to the present invention.Such polymers do not include those which contain significant amounts offunctional groups that are normally considered necessary for amino resincrosslinking--i.e. hydroxy, carboxy, mercaptan, amide. Polymers havingthe following structural features may especially be used: ##STR1## whereX is connected to a doubly bound carbon atom and is selected from thegroup consisting of R, OR, SR, NR, OSiR or SiZ₃, and R is either alkyl,alkenyl, or aryl and Z is alkyl or alkoxy. R₁, R₂, R₃, and R₅, areselected from the group consisting of hydrogen, alkyl, alkenyl or aryl,and R₄ is either alkyl, alkenyl or aryl.

A specific example is a polymer made from 1,3-isoprene monomer such that1,4-isoprene units are produced. A 1,4-isoprene unit contains structuralfeature 1 where the X is CH₃. ##STR2## Another example is an isoprenebased polymer where 3,4-isoprene monomer units result. This is anexample of structure 2 where X is CH₃ and R₁ =R₂ =R₃ =R₅ =hydrogen.##STR3## Polymers made from myrcene can exhibit several of thestructures. Myrcene (2-methyl-6-methylene-2,7-octadiene)monomer.##STR4## 7,8-myrcene mer is an example of both structure 2 and structure5. ##STR5## where X is the alkenyl group

    CH.sub.2 --CH.sub.2 --CH═C(CH.sub.3).sub.2

and R₁, R₂, R₃ and R₅ are hydrogen. ##STR6## where the `X`s are methylgroups and R₄ is the alkenyl group ##STR7## and R₁, R₂, R₃ are hydrogen.8,10-myrcene is an example of structure 1. ##STR8## where X is thealkenyl group

    CH.sub.2 --CH.sub.2 --CH═C(CH.sub.3).sub.2

The above polymers have not been considered crosslinkable with aminoresins. Surprisingly, however, I have found that specificunfunctionalized polymers are crosslinkable with amino resins. Thesepolymers may be crosslinked with themselves or with other polymers ofthe type described herein. They may also be crosslinked with polymersthat are normally crosslinkable with amino resins such as polyesters,epoxys, acrylics, alkyds, polyurethanes, etc.--a heretofore unheard ofpossibility.

A polymer is unfunctionalized if it does not contain a significantamount of functional groups. Quantitizing what constitutes a significantamount of functional groups is difficult at best because of differencesbetween various amino resins, acids, polymers, the level of these in agiven formulation, the type of functional group, the conditions of cure,etc. Also complicating the matter is the degree of cure required by theenduse application. Only a high polymer gel content may be needed toimpart a needed property, or both high gel content and a significantcrosslink density, enough to prevent appreciable swelling by a goodsolvent, may be needed.

Brushing aside the above difficulties, two "rules of thumb" are offered.First, if only high polymer gel content (greater than about 60-70%) isneeded, significant functionality is present when the number ofmilliequivalents of functionality per 100 grams of the polymer equals orexceeds the value F, where F is given by the following relationship.##EQU1## Second, if both high gel content and significant crosslinkdensity are required, significant functionality is present when thenumber of milliequivalents of functionality per gram of polymer equalsor exceeds the larger of either the F value or about 10 Meq/100 g. Forexample, if the weight average molecular weight, M_(w), of the polymeris 100,000 daltons the value of F is about 10 to about 30 Meq/100 g. Ifthe M_(w) is one million daltons, the value of F is about 1 to about 3Meq/100 g and a high gel content will be obtained at or above thislevel. The polymer will swell appreciably when exposed to a good solventunless the level of functionality equals or exceeds about 10 Meq/100 gof polymer.

Polymers containing ethylenic unsaturation can be prepared bypolymerizing one or more polyolefins, particularly diolefins, bythemselves or with one or more alkenyl aromatic hydrocarbon monomers.The polymers may be random, tapered, block or a combination of these.When the double bonds in the polyolefin are separated by three or morecarbon atoms, the ethylenic unsaturation incorporated into the polymerwill be contained in a branch extending outwardly from the main polymerchain but when the polyolefin is conjugated at least a portion of theethylenic unsaturation incorporated into the polymer may be contained inthe polymer backbone.

As is well known, polymers containing ethylenic unsaturation or botharomatic and ethylenic unsaturation may be prepared using free-radical,cationic and anionic initiators or polymerization catalysts. Suchpolymers may be prepared using bulk, solution or emulsion techniques. Inany case, the polymer may be recovered as a solid such as a crumb, apowder, a pellet or the like. Polymers containing ethylenic unsaturationand polymers containing both aromatic and ethylenic unsaturation areavailable commercially from several suppliers.

Polymers of conjugated diolefins and copolymers of one or moreconjugated diolefins and one or more alkenyl aromatic hydrocarbonmonomers are frequently prepared in solution using anionicpolymerization techniques. The present invention will, then, bedescribed by reference to such polymers. It will, however, beappreciated that any polymer containing only the desired ethylenicunsaturation or both aromatic and ethylenic unsaturation could beprocessed in accordance with the method of this invention.

In general, when solution anionic techniques are used, conjugateddiolefin polymers and copolymers of conjugated diolefins and alkenylaromatic hydrocarbons are prepared by contacting the monomer or monomersto be polymerized simultaneously or sequentially with an organoalkalimetal compound in a suitable solvent at a temperature within the rangefrom about -150° C. to about 300° C., preferably at a temperature withinthe range from about 0° C. to about 100° C. Particularly effectiveanionic polymerization initiators are organolithium compounds having thegeneral formula:

    RLi.sub.n

Wherein:

R is an aliphatic, cycloaliphatic, aromatic or alkyl-substitutedaromatic hydrocarbon radical having from 1 to about 20 carbon atoms andn is an integer of 1 to 4.

Conjugated diolefins which may be polymerized anionically include thoseconjugated diolefins containing from 4 to about 24 carbon atoms. Theconjugated diolefins which may be used in the present invention arethose which form a polymer wherein the double bond is positioned betweena tertiary carbon atom and another carbon. Examples include isoprene(2-methyl-1,3-butadiene), 2-ethyl-1,3-butadiene, 2-propyl-1,3-butadiene,2-butyl-1,3-butadiene, 2-pentyl-1,3-butadiene, (2-amyl-1,3-butadiene),2-hexyl-1,3-butadiene, 2-heptyl-1,3-butadiene, 2-octyl-1,3-butadiene,2-nonyl-1,3-butadiene, 2-decyl-1,3-butadiene, 2-dodecyl-1,3-butadiene,2-tetradecyl-1,3-butadiene, 2-hexadecyl-1,3-butadiene,2-isoamyl-1,3-butadiene, 2-phenyl-1,3-butadiene,2-methyl-1,3-pentadiene, 2-methyl-1,3-hexadiene,2-methyl-1,3-heptadiene, 2-methyl-1,3-octadiene,2-methyl-6-methylene-2,7-octadiene(myrcene), 2-methyl-1,3-nonyldiene,2-methyl-1,3-decyldiene, and 2-methyl-1,3-dodecyldiene may be used, aswell as the 2-ethyl, 2-propyl, 2-butyl, 2-pentyl, 2-hexyl, 2-heptyl,2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 2-tetradecyl, 2-hexadecyl,2-isoamyl and 2-phenyl versions of all of these dienes. Alkenyl aromatichydrocarbons which may be copolymerized include vinyl aryl compoundssuch as styrene, various alkyl-substituted styrenes, alkoxy-substitutedstyrenes, vinyl naphthalene, alkyl-substituted vinyl naphthalenes andthe like.

In general, any of the solvents known in the prior art to be useful inthe preparation of such polymers may be used. Suitable solvents, then,include straight- and branched-chain hydrocarbons such as pentane,hexane, heptane, octane and the like, as well as alkyl-substitutedderivatives thereof, cycloaliphatic hydrocarbons such as cyclopentane,cyclohexane, cycloheptane and the like, as well as alkyl-substitutedderivatives thereof, aromatic and alkyl-substituted aromatichydrocarbons such as benzene, naphthalene, toluene, xylene and the like,hydrogenated aromatic hydrocarbons such as tetralin, decalin and thelike, halogenated hydrocarbons, particularly halogenated aromatichydrocarbons, such as chlorobenzene, chlorotoluene and the like, linearand cyclic ethers such as methyl ether, methyl ethyl ether,tetrahydrofuran and the like and ketones such as methyl ketone(acetone), methyl ethyl ketone, ethyl ketone (3-pentanone) and the like.

Conjugated diolefin polymers and conjugated diolefin-alkenyl aromaticcopolymers which may be crosslinked in the present invention includepolyisoprene, natural rubber, styrene-isoprene copolymers,styrene-isoprene-styrene copolymers, polymyrcene, polymers of themonomers listed two paragraphs above, copolymers of those monomers andstyrene or the other alkenyl aromatic hydrocarbons listed in the sameparagraph and some of the unsaturated copolymers described in U.S. Pat.Nos. 3,135,716, 3,150,209, 3,496,154, 3,498,960, 4,145,298 and4,238,202, the disclosures of which patents are herein incorporated byreference. Conjugated diolefinalkenyl aromatic hydrocarbon copolymerswhich may be crosslinked in accordance with this invention also includeblock copolymers such as some of the unsaturated polymers described inU.S. Pat. Nos. 3,231,635, 3,265,765 and 3,322,856, the disclosures ofwhich patents are also incorporated herein by reference. In general,linear and branched polymers which may be crosslinked in accordance withthe present invention include those which may be represented by thegeneral formula:

    A.sub.z --(B--A).sub.y --B.sub.x

Wherein:

A is a linear or branched polymeric block comprising predominantlymonoalkenyl aromatic hydrocarbon monomer units;

B is a linear or branched polymeric block containing predominantlyconjugated diolefin monomer units which form a polymer block wherein thedouble bond is positioned between a tertiary carbon and another carbon;

x and z are, independently, a number equal to 0 or 1;

y is a whole number ranging from 0 to about 15, and the sum of x+z+y≧2.

Polymers which may be treated in accordance with this invention alsoinclude coupled and radial block copolymers such as some of theunsaturated described in U.S. Pat. Nos. 4,033,888, 4,077,893, 4,141,847,4,391,949 and 4,444,953, the disclosure of which patents are alsoincorporated herein by reference. Coupled and radial block copolymerwhich may be treated in accordance with the present invention includethose which may be represented by the general formula:

    [B.sub.x --(A--B).sub.y --A.sub.z ].sub.n --C--P.sub.n'

Wherein:

A, B, x, y and z are as previously defined and x+y+z≧1; n and n' are,independently, numbers from 1 to about 100 such that n+n'≧3;

C is the core of the coupled or radial polymer formed with apolyfunctional coupling agent; and each P is the same or a differentpolymer block or polymer segment having the general formula:

    B'.sub.x' --(A'--B").sub.y' --A".sub.z' or B".sub.x' --(A'--B').sub.y' --A'.sub.z'

Wherein:

A" is a polymer block containing predominantly monoalkenyl aromatichydrocarbon monomer units; B' is defined as B above;

A'--B" is a polymer block containing monoalkenyl aromatic hydrocarbonmonomer units (A') and conjugated diolefin monomer units (B"), theA'--B" monomer units may be random, tapered or block and when A'--B" isblock, the A' block may be the same or different from A" and B" may bethe same or different from B'; x' and z' are, independently, numbersequal to 0 to 1; and

y' is a number from 0 to about 15, with the proviso that the sum ofx'+y'+z'≧1.

The radial polymers may, then, be symmetric or asymmetric.

The crosslinking agents which are useful in the present invention areamino resins. Amino-type crosslinking resins have been commonly used tocure acrylic, polyester and epoxy resins containing functional groupssuch as hydroxyl, amide, mercaptan and carboxyl groups for many years inindustrial coatings. It has unexpectedly been found that aminocrosslinking resins are useful in curing unsaturated nonfunctionalizedpolymers as described above.

For the purposes of this invention, an amino resin is a resin made byreaction of a material bearing NH groups with a carbonyl compound and analcohol. The NH bearing material is commonly urea, melamine,benzoguanamine, glycoluril, cyclic ureas, thioureas, guanidines,urethanes, cyanamides, etc. The most common carbonyl component isformaldehyde and other carbonyl compounds include higher aldehydes andketones. The most commonly used alcohols are methanol, ethanol, andbutanol. Other alcohols include propanol, hexanol, etc. AmericanCyanamid sells a variety of these amino resins, as do othermanufacturers. American Cyanamid's literature describes three classes or"types" of amino resins that they offer for sale. ##STR9## where Y isthe material that bore the NH groups, the carbonyl source wasformaldehyde and R is the alkyl group from the alcohol used foralkylation. Although this type of description depicts the amino resinsas monomeric material of only one pure type, the commercial resins existas mixtures of monomers, dimers, trimers, etc. and any given resin mayhave some character of the other types. Dimers, trimers, etc. alsocontain methylene or ether bridges. Generally, type 1 amino resins arepreferred in the present invention.

For example, the following type 1 amino resins can be used to achievethe purpose of the present invention: CYMEL303--hexamethyoxymethylmelamine resin where R is CH₃, CYMEL 1116--amelamine-formaldehyde resin where R is a mixture of CH₃ and C₂ H₅, CYMEL1156--a melamine-formaldehyde resin where R is C₄ H₉, CYMEL1123--benzoguanamine-formaldehyde resin where R is a mixture of CH₃ andC₂ H₅, CYMEL 1170--a glycoluril-formaldehyde resin where R is C₄ H₉,CYMEL 1171--a glycoluril-formaldehyde resin where R is a mixture of CH₃and C₂ H₅, CYMEL 1141--a carboxyl modified amino resin where R is amixture of CH₃ and i-C₄ H₉, BEETLE 80--a urea-formaldehyde resin where Ris C₄ H₉, BEETLE 65--a urea-formaldehyde resin where R is CH₃. All ofthese products are made by American Cyanamid Company and are describedin its publication mentioned above along with other amino resins usefulin the present invention.

One most preferred amino resin for use in the present invention is CYMEL1170 glycoluril-formaldehyde resin where R is C₄ H₉ : ##STR10## Anothermost preferred amino resin for use in the present invention is BEETLE®80 urea-formaldehyde resin where R is C₄ H₉ whose ideal monomericstructure is depicted: ##STR11##

Since there are no functional groups, such as hydroxyl, amide, mercaptanor carboxyl groups, in the unsaturated polymers which are curedaccording the present invention, the conventional mechanism by whichthese amino resins cure functionalized polymers cannot be used toexplain the reaction in the present system. A hypothesis which I putforth as a theory herein is that the carbonium ion, ##STR12## seekselectrons at the carbon-carbon double bonds on the polymer to effectcrosslinking. Thus, the theoretical reaction mechanism is as followsusing a 1,4-isoprene monomeric unit as an example:

Reaction A: Protonation of amino resin ##STR13##

Reaction B: Dealkylation and generation resin fragment carbocation##STR14##

Reaction C: Primary crosslink reaction ##STR15##

Reaction D: Chain transfer/termination of crosslinking ##STR16## As willbe seen by reviewing the examples below, the cure results with the aminoresins of the present invention are reasonably consistent with the abovereaction mechanism.

It has been determined that the amino resins will not cure allunfunctionalized unsaturated polymers or even all conjugated dienepolymers. For instance, as shown in the examples, isoprene polymers canbe crosslinked in this manner but butadiene polymers cannot be. I havefound that these amino resins will only effectively crosslink polymersor polymer blocks wherein the double bond in the polymer or block isbetween a tertiary carbon atom and another carbon. It is theorized thatthis double bond is positioned such that when the amino resin reactswith a proton, H⁺, and the polymer or block, a positive charge iscreated at the tertiary carbon atom. It is theorized that the aminoresins will effectively crosslink in such a situation because a positivecharge at a tertiary carbon atom is the most stable type of carboniumion and because it is so stable, the crosslinking reaction is preferredand will proceed. If the positive charge is at a primary or secondarycarbon atom, such as in butadiene, the charge is not sufficiently stableto allow the crosslinking reaction to proceed. As stated above, isopreneis the preferred conjugated diene monomer for use in the presentinvention because it is readily available and widely used in commercialpolymers.

It is preferred that the amino resin be used in an amount ranging fromabout 0.5 to about 40% of the weight of the polymer if it is desired toeffect a full cure. More preferably, the amount should be from about 1to about 20% and most preferably between about 2 and about 10% becauseit is desirable to minimize appearance problems and major changes in theelasticity of the polymer.

A proton-donating acid catalyst is required to achieve the purposes ofthe present invention, i.e., crosslink the polymer using the aminoresins described above. Generally, the temperature at which this iscarried out ranges from about 200° F. to about 400° F. but lowertemperatures may be used with longer curing times. It is preferred thatthe amount of the acid catalyst used range from about 0.1 to about 4% ofthe weight of the polymer to be certain there is sufficient acid but anexcess can be undesirable. Most preferably, from about 0.5 to about 2%of the weight of the polymer is used. These ratios are sufficient ifneat polymer is used. However, if the polymer is diluted, more acid willprobably be necessary. The presence of a strong proton-donating acid isnormally required to catalyze the cross-linking reaction of many aminoresins which are useful in the present invention. However, some mediumstrength and even relatively weak acids may also be effective dependingupon the amino resins used. Generally, the most active catalyst arethose with the lowest pKa values. The following list of acid catalystwhich may be used in the present invention is arranged according toincreasing pKa value: mineral acids, Cycat® 4040 catalyst (p-toluenesulfonic acid), Cycat® 500 catalyst (dinonylnapthalene disulfonic acid),Cycat® 600 catalyst (dodecyl benzene sulfonic acid), oxalic acid, maleicacid, hexamic acid, phosphoric acid, Cycat® 296-9 catalyst (dimethylacid pyrophosphate), phthalic acid and acrylic acid (copolymerized inpolymer). Other acids which may be used are described in theaforementioned American Cyanamid Company publication. Also, 3M BrandResin Catalyst FC-520 (diethylammonium salt of trifluoromethane sulfonicacid) may be used.

Blocking agents are commonly used to prevent premature catalystactivity. Amines such as triisopropanolamine and dimethylethanolaminework by buffering the effect of the acid and block it from catalyzingthe reaction between the polymer and the amino resin. Other blockingagents include triethylamine, methyldiethanolamine, diethylethanolamine,triethanolamine, diisopropanolamine, morpholine and2-amino-2-methyl-1-propanol, water, primary, secondary and tertiaryalcohols, as well as others described in the aforementioned AmericanCyanamide Company publication.

In general, the method for carrying out the crosslinking of the blockcopolymers is as follows: Mix the block copolymer with other formulatingingredients and mix in the desired amino resin. The acid co-initiator isadded shortly before application of the formulation to the substrate.The substrate with the formulation is heated by a suitable means toabout 200° F.-400° F. to effect cure. To maintain a long package shelflife or a reasonable pot life in case of a hot melt formulation asuitable amine, alcohol or water is added to the formulation to blockthe acid and the curing reactions. Upon application of heat, theblocking agents are driven off and cure is effected.

The present invention has many advantages. One advantage is that itavoids the problem of radiation curing which primarily is the cost ofthe expensive equipment or formulation ingredients required for suchcrosslinking. This type of chemical crosslinking is a good crosslinkingsystem for a solvent-borne polymer system since the polymer has to gointo an oven to drive off the solvent, the cure or crosslinking can beachieved at the same time. The present invention could be used incombination with radiation curing wherein the polymer is partially curedwith radiation curing and the curing is completed immediately or at alater time by use of the present invention. One of the most importantadvantages of the present invention is that it allows crosslinking ofthe polymer sometime after application of the formulation. For instance,all of the ingredients could be mixed in with the polymer and a slowlydecomposing or evaporating blocking agent could be added. The acidcatalyst would not catalyze the reaction until the blocking agentdecomposes or evaporates. If the right combination of materials ischosen, the curing could take place over a period of many months. Thiscould be of advantage for uses where it is desired that the curing takeplace after the service temperature has been reached so that allstresses have been relieved (i.e. automative and electrical productadhesives).

The crosslinked materials of the present invention are useful inadhesives (including pressure sensitive adhesives, contact adhesives,laminating adhesives and assembly adhesives), sealants, coatings, films(such as those requiring heat and solvent resistance), etc. In adhesiveapplications, it may be necessary to add an adhesion promoting ortackifying resin that is compatible with the polymer. A commontackifying resin is a diene-olefin copolymer of piperylene and2-methyl-2-butene having a softening point of about 95° C. This resin isavailable commercially under the tradename Wingtack 95 and is preparedby the cationic polymerization of 60% piperylene, 10% isoprene, 5%cyclopentadiene, 15% 2-methyl-2-butene and about 10% dimer, as taught inU.S. Pat. No. 3,577,398. Other tackifying resins of the same generaltype may be employed in which the resinous copolymer comprises 20-80weight percent of piperylene and 80-20 weight percent of2-methyl-2-butene. The resins normally have softening points (ring andball) between about 80° C. and about 115° C.

Other adhesion promoting resins which are also useful in thecompositions of this invention include hydrogenated rosins, esters ofrosins, polyterpenes, terpenephenol resins and polymerized mixedolefins, lower softening point resins and liquid resins. An example of aliquid resin is Adtac LV from Hercules. To obtain good thermo-oxidativeand color stability, it is preferred that the tackifying resin be asaturated resin, e.g., a hydrogenated dicyclopentadiene resin such asEscorez® 5000 series resin made by Exxon or a hydrogenated polystyreneor polyalphamethylstyrene resin such as Regalrez® resin made byHercules. The amount of adhesion promoting resin employed varies fromabout 20 to about 400 parts by weight per hundred parts rubber (phr),preferably between about 70 to about 350 phr. The selection of theparticular tackifying agent is, in large part, dependent upon thespecific polymer employed in the respective adhesive composition.

The adhesive composition of the instant invention may containplasticizers, such as rubber extending plasticizers, or compounding oilsor organic or inorganic pigments and dyes. Rubber compounding oils arewell-known in the art and include both high saturates content oils andhigh aromatics content oils. Preferred plasticizers are highly saturatedoils, e.g. Tufflo® 6056 oil made by Arco and process oils, e.g.Shellflex® 371 oil. The amounts of rubber compounding oil employed inthe invention composition can vary from 0 to about 100 phr, andpreferably between about 0 to about 60 phr.

Optional components of the present invention are stabilizers whichinhibit or retard heat degradation, oxidation, skin formation and colorformation. Stabilizers are typically added to the commercially availablecompounds in order to protect the polymers against heat degradation andoxidation during the preparation, use and high temperature storage ofthe adhesive composition.

Combinations of primary and secondary antioxidants are preferred. Suchcombinations include sterically hindered phenolics with phosphites orthioethers, such as hydroxyphenylpropionates with aryl phosphates orthioethers, or amino phenols with aryl phosphates. Specific examples ofuseful antioxidant combinations include3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane (Irganox 1010 fromCiba-Geigy) with tris(nonylphenyl)phosphite (Polygard HR from Uniroyal),Irganox 1010 with bis(2,4-di-t-t-butyl)pentaerythritol disphosphite(Ultranox 626 from Borg-Warner),4-(4,6-bis(octylthio)-s-triazin-2-yl)amino)-2,6-di-t-butylphenol(Irganox 565) with Polygard HR, and Irganox 565 with Ultranox 626.

Additional stabilizers known in the art may also be incorporated intothe adhesive composition. These may be for protection during the life ofthe article against, for example, oxygen, ozone and ultravioletradiation. However, these additional stabilizers should be compatiblewith the essential stabilizers mentioned herein-above and their intendedfunction as taught herein.

The adhesive compositions of the present invention are typicallyprepared by blending the components at an elevated temperature,preferably between about 130° C. and about 200° C., until a homogeneousblend is obtained, usually less than three (3) hours. Various methods ofblending are known to the art and any method that produces a homogeneousblend is satisfactory. The resultant adhesives may then preferably beused in a wide variety of product assembly applications. Alternatively,the ingredients may be blended into a solvent.

The following examples are meant only to illustrate the presentinvention and not to limit it in any way.

EXAMPLE I

In this example and the following examples, three different blockcopolymers were used. Block copolymer A is a high molecular weight (1.2million) isoprene-based S-I-S star polymer (KRATON® D1320X) which isunsaturated. Block copolymer B is a very similar unsaturated starpolymer. Block copolymer H is a linear S-B-S hydrogenated polymer(KRATON® G1652) of about 50,000 molecular weight containing about 40%1,2-butadiene which has a tertiary carbon atom. The catalyst used in allcases was CYCAT® 600 catalyst, a strong proton acid catalyst which is a70% solution of dodecylbenzene sulfonic acid in isopropanol. Twodifferent crosslinking agents were used, CYMEL® 1170glycoluril-formaldehyde resin and BEETLE® 80 ureaformaldehyde resin.both of the amino resins and the acid catalyst are made by AmericanCyanamid. In this example, 90 weight percent of the polymer, 9 weightpercent of the aminoplast and 1 weight percent of the catalyst wereblended in toluene solution at 20-30 weight percent solids.

All of the solutions were rolled overnight and then cast onto 25 micronMylar to give about 75 microns of film when dry. The films were dried ina hood for two hours followed by four hours in a 40° C. vacuum oven. Thefilms were covered with silicone release paper and stored overnight at23° C. and 50% relative humidity before baking. The release paper wasused to reduce potential degradative oxidation and dirt pick up in theoven. The films were mounted on aluminum panels during the baking. Allof the films were cured in a fast recovery, electric, forced-draft airoven at the same time. The bake took place for 20 minutes at 177° C.

The degree of covalent cure obtained for each of the samples wasmeasured by use of the standard polymer gel content test developed by mefor radiation curing work and described in my article entitled"Experimental Thermoplastic Rubbers for Enhanced Radiation Crosslinkingof Hot Melt PSA's", TAPPI 1985 Hot Melt Symposium Proceedings, June1985, herein incorporated by reference. Since both the block copolymerand the crosslinking agent should become part of the network, thepolymeric factor used in the polymer gel calculation was 0.99. For theneat polymer films, the factor was 1.00. Compatibility was judged byvisual observation of the dry films before and after cure. A 0 to 10rating scale was used where clear equals 10, hazy or slightly cloudyequals 8, cloudy equals 6, very cloudy equals 4 and very cloudy plusbrown color equals 2. The results of the gel content and compatibilitytests are shown in Tables 1 and 2 below.

                  TABLE 1                                                         ______________________________________                                        Gel Content, %                                                                Polymer                                                                              Polymer Alone                                                                             CYMEL ® 1170                                                                            BEETLE ® 80                              ______________________________________                                        A      2           98            96                                           B      1           94            57                                           H      1            1             1                                           ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Compatibility                                                                 Polymer Alone   CYMEL ® 1170                                                                           BEETLE ® 80                                          Before  After   Before                                                                              After  Before                                                                              After                              Polymer Cure    Cure    Cure  Cure   Cure  Cure                               ______________________________________                                        A       10      10      8     8      6     6                                  B       10       8      8     2      10    10                                 H       10      10      6     6      6     8                                  ______________________________________                                    

Since the information available prior to this time about thesecrosslinking agents would lead one of ordinary skill in the art tobelieve that polymers without functional groups could not be crosslinkedwith these amino resins, it would be expected that no more than about 9%gel would be present in the crosslinked polymers upon baking--this dueto self cross-linking of the 9% amino resin used. It can be seen thatthe crosslinking which actually occurred with polymers A and B was farin excess of what would have been predicted since the gel contents arefar in excess of 9%. This shows that the hydrogenated butadiene polymerdoes not crosslink even though it has a tertiary carbon. There was nodouble bond and therefore no crosslinking. Most of the compatibilityresults are also good, showing that the curing has no effect on thevisual compatibility of the polymers.

EXAMPLE II

The present experiments were carried out in accordance with the sameprocedure given for Example I with the exception that two different baketemperatures were utilized, two different levels of catalyst wereutilized and two different antioxidants were added at two differentlevels. These experiments were carried out using block copolymer A,CYMEL® 1170 resin, CYCAT® 600 catalyst, Polygard® HR antioxidant, madeby Uniroyal, and Antioxidant 330 made by Ethyl Corporation.

The different formulations are shown in Table 3. The results are shownin Table 4.

                  TABLE 3                                                         ______________________________________                                               Formulations                                                                  4.1  4.2    4.3    4.4  4.5  4.6  4.7  4.8                             ______________________________________                                        Polymer A                                                                              90.9   90.0   90.0 89.1 90.0 89.1 89.1 88.2                          CYMEL 1170                                                                             9.1    9.0    9.0  8.9  9.0  8.9  8.9  8.8                           CYCAT 600                                                                              0      1.0    0    1.0  0    1.0  0    1.0                           Polygard HR                                                                            0      0      1.0  1.0  0    0    1.0  1.0                           Antioxidant                                                                            0      0      0    0    1.0  1.0  1.0  1.0                           330                                                                           Total (grams)                                                                          100.0  100.0  100.0                                                                              100.0                                                                              100.0                                                                              100.0                                                                              100.0                                                                              100.0                         Toluene  150    150    150  150  150  150  150  150                           (grams)                                                                       Bake     149    177    177  149  177  149  149  177                           Temperature                                                                   (°C.)                                                                  ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                                    Formulations                                                                  4.1 4.2    4.3   4.4 4.5 4.6  4.7 4.8                             ______________________________________                                        % Gel         1     99,97  0   88  0,0 100  1   93,96                         Compatibility Rating                                                          Before Cure   6     10,10  6   10  6,6 8    6   6,6                           After Cure    6     10,10  6   10  6,6 8    6   6,6                           ______________________________________                                    

The above results prove that the acid catalyst is absolutely necessaryto achieve crosslinking since formulations 4.1, 4.3, 4.5 and 4.7, whichdid not contain acid catalysts, did not crosslink at all. Thecrosslinking of the other formulations was carried out quite well asevidenced by the percent gel and the compatibility ratings. This showsthat the lower bake temperature and the presence of antioxidant has nodetrimental effect on the crosslinking.

EXAMPLE III

All of the samples contained two antioxidants, Polygard® HR and Irganox®1010 antioxidant made by Ciba-Geigy. The amount of the amino resin, theamount of the acid catalyst, the bake temperature and the bake time werevaried.

In this example, the procedure of Example I was modified. Theformulation ingredients, as shown in Table 5, except for the acidcatalyst, were dissolved in the solvent and rolled overnight. A toluenesolution of the acid catalyst was mixed in by hand about five minutesbefore the formulations were cast. The formulations were solvent castonto Mylar sheets to provide about 3 mils of dry polymer film. The filmswere dried one hour in a hood but were not placed in a vacuum oven,covered or aged overnight at constant temperature and humidity forbaking. The films were mounted on quarter inch thick Pyrex glass panelsduring the baking in an electric forced air oven with good recoverytime. All of the 121° C. samples were cured at the same time and all ofthe 149° C. samples were cured at another time. The gel results obtainedare given in Table 6.

                  TABLE 5                                                         ______________________________________                                               Formulations                                                                  5.1  5.2    5.3    5.4  5.5  5.6  5.7  5.8                             ______________________________________                                        Polymer A                                                                              94.5   89.5   94.0 89.1 94.5 89.5 94.0 89.1                          CYMEL 1170                                                                             4.0    9.0    4.0  8.9  4.0  9.0  4.0  8.9                           Irganox 1010                                                                           0.5    0.5    0.5  0.5  0.5  0.5  0.5  0.5                           Polygard HR                                                                            0.5    0.5    0.5  0.5  0.5  0.5  0.5  0.5                           CYCAT 600                                                                              0.5    0.5    1.0  1.0  0.5  0.5  1.0  1.0                           Total (grams)                                                                          100.0  100.0  100.0                                                                              100.0                                                                              100.0                                                                              100.0                                                                              100.0                                                                              100.0                         Toluene  233.3  233.3  233.3                                                                              233.3                                                                              233.3                                                                              233.3                                                                              233.3                                                                              233.3                         (grams)                                                                       Bake     121    121    121  121  149  149  149  149                           temperature                                                                   (°C.)                                                                  Bake time                                                                              10     20     20   10   20   10   10   20                            (min.)                                                                        ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Formulations                                                                          5.1     5.2   5.3   5.4 5.5   5.6 5.7   5.8                           ______________________________________                                        % Gel   0       0     96    98  92    95  97    100                           ______________________________________                                    

The results show that the amount of aminoplast and the bake time had nosignificant effect on the degree of covalent network formation(cross-linking) as measured by percent gel. Both the high levels and thelow levels cured well. However, there was some effect of the catalystlevel and the bake temperature. The combination of 0.5% acid catalystand 121° C. bake did not produce curing. The reason for this is that thetemperature was too low for the small amount of catalyst used.

EXAMPLE IV Improved Laminating Adhesives

Formulations A, B and C (Table 7) were prepared by weighing all of theingredients, except for the CYCAT 600 catalyst, into glass bottles androlling the bottles for 24 hours to make a uniform solution. The CYCAT®600 catalyst was then added and mixed in for 2.5 minutes and then eachsolution was allowed to sit for 30 minutes before casting thin films.Films were applied to silicone release paper using a Bird applicator.The films were allowed to dry for about 24 hours in a hood. The dry filmthickness was about 1.5 mils. Each film was covered with a sheet of 100%cotton paper and then the paper and adhesive were pulled off thesilicone release paper. Each adhesive film was covered with a secondsheet of cotton paper to produce a laminate having the adhesive film asthe middle layer. Each sheet of laminate was cut in half. One half wascured for 10 minutes at 250° F. in a 12 ton Carver Press Model C using aone ton pressure and the other half was cured for 10 minutes at 300° F.using the same pressure. One inch diameter discs were cut from each ofthe laminates and were placed in 100 mls of toluene in 4 ounce bottles.The bottles containing the laminates were rolled at room temperature for24 hours. Formulations A and B, which contained the isoprene based blockpolymer A and CYMEL® 1170 resin, held the laminates together, whileformulation C, which did not contain CYMEL® 1170 resin, completelydissolved in the toluene and allowed the two layers of paper tocompletely separate from each other. See Table 8.

                  TABLE 7                                                         ______________________________________                                        Ingredient   A           B       C                                            ______________________________________                                        Block copolyer A                                                                           42.7        90.0    47.2                                         Wingtack ® 95.sup.1                                                                    32.0        0.0     35.3                                         Adtac ® B10.sup.2                                                                      15.0        0.0     16.6                                         BHT.sup.3    0.43        0.46    0.47                                         Polygard ® HR                                                                          0.43        0.46    0.47                                         CYMEL ® 1170                                                                           8.5         8.2     0.0                                          Toluene      233.3       233.3   233.3                                        CYCAT ® 600*                                                                           0.85        0.91    0.00                                         ______________________________________                                         *Added as a 5% solution in toluene.                                           .sup.1 Wingtack 95 is a high softening point tackifying resin.                .sup.2 Adtac ® B10 is a low softening point tackifying resin.             .sup.3 Butylated hydroxy toluene.                                        

                  TABLE 8                                                         ______________________________________                                        Laminate Appearance After Toluene Soak                                        Press                                                                         Temperature                                                                              A           B       C                                              ______________________________________                                        250° F.                                                                           intact      intact  paper loose                                    300° F.                                                                           intact      intact  paper loose                                    ______________________________________                                    

EXAMPLE V

The process of the present invention was carried out with severaldifferent polymers according to the procedure set forth below and thecrosslinked samples were evaluated for gel content. The formulations areset forth in Table 9 and the experimental results are set forth in Table10. Block copolymer C is a radial butadiene S-B-S block copolymer(KRATON® D1184) with a molecular weight of about 200,000 and wasprimarily comprised of 1,4-butadiene monomer units which have a doublebond but no tertiary carbon. Block copolymer D resin is a linearisoprene S-I-S block copolymer (KRATON® D1107) with a molecular weightof about 150,000. Block copolymer E is a partially hydrogenatedbutadiene-isoprene (S-B/I-S) block copolymer which contains about 6-7%unhydrogenated isoprene units and is primarily 1,4-isoprene with amolecular weight of 50,000. CYMEL® 303 resin is ahexamethoxymethylmelamine resin.

                  TABLE 9                                                         ______________________________________                                        Ingredients (%)                                                                           A      B      C    D    E    F    G                               ______________________________________                                        Block Copolymer A                                                                         94     94     94   --   --   --   98                              Block Copolymer C                                                                         --     --     --   94   --   --   --                              Block Copolymer D                                                                         --     --     --   --   94   --   --                              Block Copolymer E                                                                         --     --     --   --   --   94   --                              Cymel ® 1170                                                                          4      --     --   4    4    4    --                              Cymel ® 303                                                                           --     4      --   --   --   --   --                              Beetle ® 80                                                                           --     --     4    --   --   --   --                              Irganox ® 1010                                                                        0.50   0.50   0.50 0.50 0.50 0.50 0.50                            Polygard ® HR                                                                         0.50   0.50   0.50 0.50 0.50 0.50 0.50                            Toluene     300.00 300.00 300.00                                                                             300.00                                                                             233.30                                                                             300.00                                                                             300.00                          Cycat ® 6OO                                                                           1.00   1.00   1.00 1.00 1.00 1.00 1.00                            ______________________________________                                    

Procedure:

The test formulations were prepared by adding all the ingredients,except for the CYCAT® 600 catalyst, to glass jars and rolling overnightto dissolve the mixtures. The catalyst was added as a 5% solution intoluene just before casting the test films. Specifically, the catalystwas hand mixed into the solution for 5 minutes and then the solution wasallowed to set for about 10 minutes before application to 1 mil Mylarsheets. The films were placed in a hood for about 1 hour to partiallydry before baking. Final baked film thickness of the polymeric films wasabout 75 microns. Bake conditions were 20 minutes at 149° C. using aforced-draft electric oven.

                  TABLE 10                                                        ______________________________________                                        Gel Contents on Heat Cured Kraton ® Rubber                                         Gel        Solution Fluidity                                         Formulation                                                                              Content      7 Days*  108 Days                                     ______________________________________                                        A          100          gel      gel                                          B           0           fluid    fluid                                        C          98           gel      gel                                          D           2           fluid    fluid                                        E          85           fluid    fluid                                        F           0           fluid    fluid                                        G          27           fluid     fluid**                                     ______________________________________                                         *Day after addition of the Cycat ® 600                                    **Turned dark brown color as did the Cycat ® 600 solution used.      

The results show that the unsaturated isoprene polymer cured quite wellwith preferred amino resins, Cymel® 1170 and Beetle® 80 resins (A andC), but that the Cymel® 303 resin was ineffective under these conditions(formulation C). Also, it is quite apparent that the linear unsaturatedisoprene polymer D cured very well with the preferred amino resin,Cymel® 1170 resin (formulation E). In contrast, the radial butadienepolymer with few tertiary carbons and no double bonds attached totertiary carbons did not cure at all (formulation D) even with thepreferred amino resins. The partially hydrogenated polymer (formulationF) did not cure at all because it contained only a small amount ofunhydrogenated isoprene. Formulation G without amino resin curedineffectively. Therefore, it is shown that the isoprene polymers curevery well while the hydrogenated polymers and the butadiene polymers donot cure at all. Those formulations that cured well also lacked longterm room temperature package stability, since the solution formulationgelled each time. This indicates that the curing will occur at roomtemperature given enough time. This feature would make them useful incontact assembly adhesives.

EXAMPLE VI

In this example, the block copolymer A was crosslinked with a variety ofamino resins and several different catalysts. In most cases, thecatalyst was blocked with diisopropanolamine. From the results, it isapparent that this blocking agent had too high a boiling point, it wasnot driven off fast enough during the experiment because it effectivelyblocked the activity of the catalyst in most of these experiments. Forcompleteness, the formulations are shown in Table 11 and theexperimental results in Table 12. The procedure is set forth below.

                                      TABLE 11                                    __________________________________________________________________________               FORMULATIONS:                                                      Ingredients                                                                              H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X                  __________________________________________________________________________    Block Copolymer A                                                                        94 94 94 94 94 94 94 94 94 94 94 94 94 94 94 94 94                 Cymel ® 1170                                                                         4  4                                                               Cymel ® 303  4                                                            Cymel ® 327     4  4                                                      Cymel ® 370           4  4                                                Cymel ® 1116                4                                             Cymel ® 1123                   4                                          Cymel ® 1125                      4                                       Cymel ® 1141                         4                                    Cymel ® 1156                            4                                 Cymel ® 1158                               4  4                           Cymel ® 1171                                     4                        Beetle ® 80                                         4                     Beetle ® 65                                            4                  Irganox ® 1010                                                                       .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5                 Polygard HR                                                                              .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5                 Toluene    300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                5% Cycat ® 600                                                                       1.0                                                                5% Cycat ® 600                                                                          1.0                                                                              1.0   1.0   1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0   1.0                                                                              1.0                                                                              1.0                                                                              1.0                (Blocked)                                                                     5% Cycat ® 269-9                                                                              1.0   1.0                  1.0                            __________________________________________________________________________

Procedure:

The sample preparation, coating and curing were done in the same manneras in the Example V. The diisopropanolamine was added to the 5% solutionof the CYCAT® 600 in toluene. A 1:1 stochiometric ratio was used. Bakingconditions remained 20 minutes at 149° C.

                  TABLE 12                                                        ______________________________________                                        Gel Contents of Heat Cured KRATON ® Rubber                                Formulation    Gel Content                                                    ______________________________________                                        H              98                                                             I              1                                                              J              1                                                              K              2                                                              L              0                                                              M              1                                                              N              1                                                              O              3                                                              P              56                                                             Q              12                                                             R              8                                                              S              65                                                             T              1                                                              U              1                                                              V              2                                                              W              83                                                             X              2                                                              ______________________________________                                    

The addition of the blocking agent had the expected effect on thesolution formulations. All of the solutions remained fluid when storedat 25° C. for 99 days. Sample H which was not blocked does show verygood results in terms of gel content. Samples I, J, L, N, O, Q, R, U, Vand X all used blocked catalyst and the results are very poor. Samples Pand S show partial gelling which may be due to partial elimination ofthe blocking agent. Sample W used a blocking agent and the results werereasonably good indicating that in this case, most of the blockingagents had been drive off prior to reaction with the amino resin.Formulations K, M and T utilized the relatively weak catalyst Cycat®269-9 resin. It is thought that the lack of success may partially be dueto the use of this relatively weak catalyst. However, there aresituations in which relatively weak catalyst might be very useful in theperformance of the present invention (for example, see Example IXbelow).

EXAMPLE VII

In this series of experiments, several different polymers were testedwith several different amino resins. The catalyst was not blocked in anyof these tests. The formulations are shown in Table 13 and theexperimental results are shown in Table 14. All preparation, coating andbaking conditions were the same as in Example V. Bake temperatureremained at 20 minutes at 149° C.

                                      TABLE 13                                    __________________________________________________________________________              FORMULATIONS: % (25% solids)                                        Ingredients                                                                             AA BB CC DD EE FF GG HH II JJ KK LL MM NN                           __________________________________________________________________________    Block Copolymer A                                                                       94 94 94 94 94 94 94 94 94 94                                       Block Copolymer C                       94 94                                 Block Copolymer D                             94 94                           Cymel ® 1156                                                                        4                                                                   Cymel ® 1116                                                                           4                                                                Cymel ® 1158                                                                              4                                                             Cymel ® 1170   4                                                          Cymel ® 1171      4                                                       Cymel ® 1123         4                                                    Cymel ® 1125            4                                                 Cymel ® 1141               4                                              Beetle ® 80                   4     4     4                               Beetle ® 65                      4     4     4                            Irganox ® 1010                                                                      .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5                           Polygard ® HR                                                                       .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5                           Toluene   300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                                                                              300                          Cycat ® 600                                                                         1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                                                                              1.0                          __________________________________________________________________________

                  TABLE 14                                                        ______________________________________                                        Gel Contents of Heat Cured KRATON ® Rubber                                              Solution Fluidity                                                                         Film                                                Formulation                                                                            Gel Content                                                                              3 Days*  87 Days*                                                                             Appearance                                ______________________________________                                        AA       100        fluid    fluid  2                                         BB       100        fluid    fluid  2                                         CC        46        fluid    fluid  2                                         DD       100        gel      gel    9                                         EE       100        gel      gel    6                                         FF       100        fluid    fluid  2                                         GG        99        fluid    fluid  2                                         HH        86        fluid    fluid  2                                         II       100        gel      gel    9                                         JJ        99        rubbery  gel    6                                         KK        0         fluid    fluid  1                                         LL        1         fluid    fluid  1                                         MM        70        fluid    gel    9                                         NN        56        fluid    fluid  9                                         ______________________________________                                         *Days after addition of CYCAT ® 600.                                 

Again, it is shown that the butadiene polymer (formulations KK and LL)is not crosslinked when treated according to the present invention. Inaddition, it can be seen that most of the amino resins used worked wellwith the isoprene star polymer and that the linear isoprene polymer wascrosslinked reasonably well.

EXAMPLE XIII

Example XIII was designed to provide information on the effectiveness ofusing an alcohol as the blocking agent and the ability of a weak acid tofunction as the co-initiator.

The specific polymer/amino resin formulations shown in Table 15 wereprepared and tested. The sample preparation, coating and curing weredone in the same manner as in Example V. The Test results are given inTable 16.

                  TABLE 15                                                        ______________________________________                                                    Formulations                                                                  A    B          C      D                                          ______________________________________                                        Polymer A     94.0   94.0       94.0 94.0                                     CYMEL 1170    4.00   4.00       4.00 4.00                                     Irganox 1010  0.50   0.50       0.50 0.50                                     Polygard HR   0.50   0.50       0.50 0.50                                     n-Butanol     --     75         --   --                                       Toluene       300    225        300  300                                      CYCAT 600     1.00   1.00       --   --                                       CYCAT 296-9   --     --         1.00 2.00                                     ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                                     Formulations                                                                  A    B         C      D                                          ______________________________________                                        % Gel Content  100    100       1    87                                       Film*                                                                         Appearance, rating                                                                            8      7        4     4                                       Solution Fluidity                                                             7 days**       gel    fluid     fluid                                                                              fluid                                    60 days        gel    fluid     fluid                                                                              fluid                                    ______________________________________                                         *After baking.                                                                **After acid addition.                                                   

The addition of the butanol to the solvent system (Formulation B)prevented the gellation in the package without interfering with thecure. The weak acid CYCAT® 296-9 was able to co-initiate the curereactions when used at the 2% level (Formulation D) but not at the 1%level of addition (Formulation C). However, the cure was not as good asthat normally obtained by using the CYCAT® 600.

EXAMPLE IX

SIS based hot melt pressure sensitive adhesives (PSA's) must often bekept in open stirred tanks at customer facilities for periods as long as24 or 48 hours at 177° C. This causes the viscosity to decreasesubstantially due to chain scission of the SIS polymer. It would be verydesirable if these viscosity changes did not occur. If a competing chainbuilding or crosslinking reaction could be made to occur at about thesame rate as the chain scission reaction over a reasonable range oftemperature and time conditions, at least the viscosity would appear notto change significantly. The present experiment was done to determinewhether small amounts of the amino resins have potential in this regard.

The PSA formulations given in Table 17 were prepared in a sigma blademixer, oven aged at 177° C. for 24 hours and tested for viscosity. Anumber of the samples were completely replicated. Polygard® antioxidantinstead of Polygard HR® antioxidant was deliberately used. It was hopedthat the Polygard® antioxidant, a phosphite, would generate phosphoricacid during oven aging and catalyze the crosslinking resins as needed.For oven aging, part (100 grams) of the freshly prepared hot melt waspoured into a 200 ml tall form glass beaker, covered with aluminum foil,and placed in an electric forced draft air oven. Hot melt viscositymeasurements at 177° C. were made on a Brookfield Thermocel Viscometerusing a No. 29 spindle at low rpm.

                  TABLE 17                                                        ______________________________________                                        Formulations for Improved SIS PSA Hot Melt Stability                                     Formulations                                                                  8.1   8.2     8.3     8.4   8.5                                    ______________________________________                                        F/G*         24.9    24.6    24.6  24.6  24.6                                 Polygard ®                                                                             0.25    0.25    0.25  0.25  0.25                                 Ionol ®  0.25    0.25    0.25  0.25  0.25                                 Escorez ® 5300 resin                                                                   59.7    59.1    59.1  59.1  59.1                                 Tufflo ® 6056 oil                                                                      14.9    14.8    14.8  14.8  14.8                                 Cymel ® 303                                                                            0       1.5     0     0     0                                    Cymel ® 1156                                                                           0       0       1.5   0     0                                    Cymel ® 1170                                                                           0       0       0     1.5   0                                    Beetle ® 80                                                                            0       0       0     0     1.5                                  TOTAL        100.0   100.0   100.0 100.0 100.0                                ______________________________________                                         The ingredients are listed in their order of addition to the sigma blade      mixer. The amino resin was premixed into the oil. The total mixing time o     each formulation was 35 minutes, with the amino resin/oil blend added         about 30 minutes into the mix.                                                *65/35 blend of KRATON ® D1111 block copolymer F and KRATON ®         D1117 block copolymer G.                                                 

                  TABLE 18                                                        ______________________________________                                        Melt Viscosity Results                                                                                   Melt Viscosity                                                                177 deg. C.                                        Form- Crosslinking Initial Aged**     Retention                               ulation                                                                             resin        (cp)    (cp)       (%)                                     ______________________________________                                        8.1   none         3550    1810       51                                      8.1   none         4340    1990       46                                      8.2   Cymel ® 303                                                                            4440    gel        infinite                                8.2   CymeI ® 303                                                                            4050    6040       149                                     8.3   Cymel ® 1156                                                                           gel     gel        infinite                                8.4   Cymel ® 1170                                                                           4270    1980       46                                      8.4   Cymel ® 1170                                                                           3990    3710       93                                      8.5   Beetle ® 80                                                                            2780    1800       65                                      ______________________________________                                         *Many of the formulations were duplicated. This involved completely           remaking them on the sigma blade mixer and testing on different days.         **Aged for 24 hours at 177° C.                                         # The sample began crosslinking in the viscometer.                       

The viscosity results are given in Table 18. The Cymel® 303 and Cymel®1156 resins were surprisingly active and gelled the adhesives. Thus itcan be seen that Cymel® 303 which did not work well in the earlier shortterm tests does work to crosslink (form a gel) in an aging test athigher temperature. Additionally, this experiment utilized therelatively weak acid, phosphoric acid, so it can be seen that there areapplications where weak acids can be used in the present invention.

EXAMPLE X Use of Triflic Acid Salt

The purpose of this experiment was to determine the effectiveness ofFC-520 as a co-initiator for the amino resin/polymer cure reactions.FC-520 is a 60% solution of the diethylammonium salt oftrifluoromethanesulfonic (triflic) acid in water and diethylene glycolmonoethyl ether and is supplied by the 3M Company. FC-520 is recommendedfor use in coating formulations that contain both epoxy resins andconventional functionalized polymers that undergo condensation cure withamino resins. The FC-520 is reported to be able to activate the requireddual cure. It initiates the cationic chain reaction through the epoxygroups and also catalyzes the reaction between the amino resin andhydroxyl bearing polymer.

The formulations tested are shown in Table 19. The FC-520 was usedwithout an amino resin present in Formulation 9B to test for the abilityof the FC-520 to promote cure. In Formulation 9C, it was tested as aco-initiator with CYMEL® 1170. FC-520 is more polar and much moreexpensive than CYCAT® 600. Consequently, the solvent system used was the25/75 n-butanol/toluene solvent system and the level of the FC-520 wasrestricted to only 0.5% of the solids. Table 20 shows the results.

                  TABLE 19                                                        ______________________________________                                        Use of Triflic Acid Salt                                                                 Formulation ID                                                                9A        9B      9C                                               ______________________________________                                        Polymer A    99.0        98.5    94.5                                         CYMEL ® 1170                                                                           --          --      4.00                                         Irganox ® 1010                                                                         0.50        0.50    0.50                                         Polygard ® HR                                                                          0.50        0.50    0.50                                         n-Butanol    75          75      75                                           Toluene      225         225     225                                          FC 520       --          0.50    0.50                                         ______________________________________                                    

                  TABLE 20                                                        ______________________________________                                                    Formulation ID                                                                9A       9B      9C                                               ______________________________________                                        FC 520        0          .5%       .5%                                        CYMEL ® 1170                                                                            0          0       4%                                           % Gel Content 0          1       61                                           Film*                                                                         Appearancc, rating                                                                          7.5        5.5     6.5                                          Solution Fluidity                                                             7 days**      fluid      fluid   fluid                                        60 days       fluid      fluid   fluid                                        ______________________________________                                         *After baking.                                                                **After acid addition.                                                   

Thus, the combination of the weak catalyst (FC-520) and the amino resinis shown to have the ability to reasonably effectively crosslink thepolymer.

I claim:
 1. A method of curing unsaturated polymers which have less than10 Meq/100 grams of polymer of functional groups which undergo acrosslinking reaction with amino resins and which contain at least onedouble bond between a tertiary carbon atom and another carbon withunsaturated polymers which have 10 Meq/100 grams of polymer or more ofsuch functional groups, said method consisting essentially of mixingsuch polymers with an amino resin in the presence of a proton-donatingacid catalyst.
 2. The method of claim 1 wherein the polymers with 10Meq/100 grams of polymer or more of functional groups are selected fromthe group consisting of polyesters, epoxys, acrylics, alkyds andpolyurethanes.
 3. A cured polymer made according to the process ofclaim
 1. 4. An adhesive made with the cured polymer of claim
 3. 5. Asealant made with the cured polymer of claim
 3. 6. A coating made withthe cured polymer of claim
 3. 7. A film made with the cured polymer ofclaim 3.